Radiotelephone transmitting system.



W. T. DITCHAIVI. RADIOTELEPHONE TRANSMITTING SYSTEM.

APPLICATION FILED IUNEZO, I9I4.

Patented Feb. 29, 1916.

maeee,

W/T/VEeSSiS! WILLIAM THEODORE DITGHAM, OF TWICKENHAM, ENGLAND.

BADIOTELEPHONE 'JPRANSMIIII'IUSING- SYSTEM.

Specification of Letters Patent.

Patented Feb. 29, 1916.

, Application filed June 20, 1914. Serial No. 846,298.

To all whom it may concern Be' it known that .1, WILLIAM THEoDonE DITCHAM, subject of the King of Great Britain, residing at Kildary, Lebanon Park,

Twickenham', in the county of Middlesex, England, have invented certain new and useful Improvements in Radiotelephone Transmitting Systems, of which the following is a specification.

This invention relates to the production of electromagnetic oscillations of a group frequency approaching or exceeding the limits of audibility, for use, more especially 1n radio telephony, but also in radio telegraphy. For this purpose the known arrangement is employed of a short cooled spark gap having parallel metallic electrodes, supplied with direct current through inductive resistance, and shunted by a condenser and connected to an inductance, the inductance being so tightly coupled to a radiating aerial or to another circuit as to cause the energy in the shunt circuit to be rapidly abstracted therefrom.

It has already been proposed in ashock excitation wireless system to employ a spark gap, having sparking surfaces of large area in an atmosphere of carbon dioxid gas. This arrangement however is unsuitable for the purpose of producing discharges of a group frequency and constancy suitable for wireless telephony.

According to the present invention, the discharge of the oscillation discharger or spark gap takes place between surfaces of small area in a current of carbon dioxid gas. The discharger may consist of a pair or a series of pairs of the metallic electrodes. I find that by employing such an oscillator or discharger in conjunction with suitable circuits, electromagnetic waves of high group frequency may be radiated, which have a very definite wave length, small damping, and are of great regularity and constant intensity and very suitable for use in radio telephony.

The electrodes of the discharger may be of various forms and sizes, consistent with having sparking surfaces of small area, and

ing properties or alternatively are water cooled or otherwise prevented from becoming overheated by the discharges in any known manner.

Preferably the electrodes are provided with a screw or other suitable device for adjusting the distance between the sparking surfaces, which should not exceed a fraction of a millimeter, and are inclosed in an airtight chamber through which the carbon dioxid is caused to flow.

It is desirable to make the gap electrodes of as small a cross section as possible consistent with freedom from distortion by the heat of the discharge, in order that the electro-static capacity of the gap may be reduced to a minimum and the discharge be confined to a small lateral limit of movement. Several such dischargers may be used in series varying in number according to the voltage of the direct current supply, for instance, by using a supply at a voltage of 1000, for such discharges in series may be conveniently operated.

Apparently the oscillations in the condenser shunt circuit associated with the discharger are in the nature of strongly damped or quenched impulses, and in the operation of the invention it is not necessary or desirable for the natural frequency of the condenser shunt circuit to be the same as, or a harmonic of, the natural frequency of the aerial circuit. 1

It appears to be desirable for the condenser circuit to have a frequency considerably less than the aerial circuit, and for the aerial circuit to be so closely coupled to the,

condenser circuit that the energy in the said condenser circuit is rapidly transferred to the aerial.

In certain cases when the difference between the natural frequency of the discharge circuit and the radiating circuit is considerthe gaps an inductance tightly coupled to or included in the aerial circuit.

In place of the condenser circuit directly energizing the aerial as above described, an

intermediate circuit coupled to the aerial may be excited, and the said intermediate circuit may either contain a condenser and be tuned to the frequency of the aerial or be an aperiodic circuit Without such condenser, in which latter case a microphone may be inserted in the intermediate circuit for purposes of radio telephony.

A spark-gap discharger and diagrams of arrangements according to the present invention are illustrated on the accompanying drawing, in which Figure 1 is a sectional elevation of the spark-gap discharger. Figs. 2-5 are diagrams showing alternative connections.

Referring to Fig. 1, the spark-gap discharger 11, consists of a pair of spark-gap electrodes 6 6 arranged vertically superposed. The lower end of the bottom electrode I) is mounted in a base plate 0 and each electrode is provided with a series of radial cooling flanges d. A block e of insulating material formed with a central recess 7, coaxial with the electrodes, is mounted on a flange g at the upper end of the bottom electrode 6 The upper surface of the block a and the recess f are covered by an insulating annular cover plate h. A flange plate i is secured thereto and is internally screw-threaded, into which the upper electrode 6 screws, being fitted at its upper end with amilled head j of insulating material. The covered recess f in the block e constitutes the gas chamber and is rovided with inlet and outlet pipes 70 70 or the carbon dioxid gas, which is supplied from a high pressure gas bottle. The actual sparking terminals consist of small blocks 6 held in recesses in the opposing ends of the electrodes b 12 which latter are of larger diameter than the terminal blocks 1). The carbon dioxid gas cools the spark-gap, this being promoted by the low temperature of the gas owing to its expansion on escape from the high pressure gas bottle.

Referring to the diagrams :'na is a source of direct current electricity, n a re sistance and o inductances in series therewith.

a is the spark-gap in an atmosphere of CO In Figs. 2 and 3, a condenser 39 and an inductance q are in shunt with the spark-gap a, the inductance 9 being either tightly coupled to an inductance 1' of the aerial s, Fig. 2, or to an inductance t of an aperiodic circuit containing an inductance a, tightly coupled to the inductance r of the aerial s, and containing a microphone '11, Fig. 3.

In the alternative arrangements shown in Figs. 4 and 5, the spark-gap a or a pair of spark-gaps a are in the circuit of the inductance g, in shunt with the condenser 72, the

inductance 9 being between the spark-gaps 1. In a spark gap discharger for wireless telephony, a base, an electrode mounted on said base, radial cooling flanges on said electrode, a flange near the upper end of said electrode, a centrally recessed block of insulating material supported on said flange, inlet and outlet pipes in said block, a cover of insulating material on said block, an internally screw-threaded flange plate on said cover above said electrode, an electrode screwed into said flange plate, radial cooling flanges on said second electrode and a head'of insulating material on said second electrode.

2. In a spark gap discharger for wireless telephony, a base, an electrode mounted on said base, radial cooling flanges on said electrode, a flange near the upper end of said electrode, a centrally recessed block of insulating material supported on said flange, inlet and outlet pipes in said block, a cover of insulating material on said block, an internally screw-threaded flange plate on said cover above said electrode, an electrode screwed into said flange plate, radial cooling flanges on said second electrode, a head of insulating material on said second elec trode and small terminal blocks fitted in recesses in the adjacent ends of said electrodes.

In testimony whereof I ailix my signature in presence of two witnesses.

WILLIAM THEODORE DITGHAM.

Witnesses: I

ROBERT ARTHUR SMITH, RoBT. ALFRED BLAKE. 

